Fix writeXMLHeader overloading with multi-inheritance

The previous patch only partially resolved the issue. We have
multi-inheritance here and both base classes contain writeXMLHeader, yet
both have different signatures.

Resolve all this issues.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
Merge pull request #5737 from davidlt/final-clang-cleanup-for-boost

Fix writeXMLHeader overloading with multi-inheritance